LEO stuff is more complex because the Horizon keeps getting in the way!!

Regarding directionality, then yes, pointing your antenna the right way is of course important, but no antenna is truly collimated, so the beam of radiation spreads out into a cone, and so by the time it gets to the space craft, it’s wide, and hence absolute positional accuracy iless critical. Of course, that also spreads out your RF power and needs a higher transmission power, so it’s a compromise.

For example, the transmitter on Voyager 1 is just 22 watts, which is roughly the same amount of power as one of the indicator light bulbs in your car! Because it’s 18B miles away mind, we need a 70M dia dish to be able to resolve that signal above the noise floor, and when transmitting up to the craft, we need to send with MUCH more power (because it only has a 3.7M dish). Current round trip for those signals is 33hrs.

true about the horizon.
was handy having a satellite to satellite link (LEO to GEO to ground) on the last project, and that way you can have as much as 1 hour of uninterrupted comms in a 100 minute orbit.
sadly next project has the horizon in the way issue again.

where are the pics from the surface???
conspiracy – they are not showing them because its full of REPLICATORS
http://img3.wikia.nocookie.net/__cb20080425065649/stargate/images/3/31/Replicator.JPG" alt="" title="" class="bbcode-image" />

For older sci-fi fans, the Philae lander looks like:

Because its actually:

IT’S STABLE!!!!

http://www.bbc.com/news/science-environment-30034060

OOOHH I wonder if theyll find an experimental starship whose phase shifting cloaking device failed?

http://img3.wikia.nocookie.net/__cb20120909161428/memoryalpha/en/images/1/1b/USS_Pegasus.jpg

This is what you want, on board image just posted on twotter

http://t.co/EYSlRFjQBb

Now that I’m safely on the ground, here is what my new home #67P looks like from where I am. #CometLanding pic.twitter.com/gFmt8Ldvpa

— Philae Lander (@Philae2014) November 13, 2014

From that link

“The full panoramic from CIVA will be delivered in this afternoon’s press briefing at 13:00 GMT/14:00 CET.”

Also, there is some speculation that the first “bounce” when it tried to land was almost 1 km high!

IT’S STABLE!!!!

Some of those Reader’s Comments though…

Another huge waste of money to keep poor quality scientists employed on the only trivia they are capable of being involved in …. and they couldn’t even do that well ! These people should try working on projects that would have to meet strict business case criteria and suffer the consequences of their failure (like those of us in the real world do) to deserve respect.
…
Really incredible how much money is being wasted on this pie in the sky meaningless expedition into emptiness. It is the triumph of nihilism that the bankrupt EU can still bankroll complete wastage on this scale. It is time we brought into focus how many lives could have been saved in European hospitals for the cost of this space adventure?

*shakes head sadly*

Fortunately most folk seem to recognise what an amazing achievement it is.

I actually performed 3 landings,15:33, 17:26 & 17:33 UTC.

I did laugh at the rather overexcited lady from the Open University

That wasn’t over excitement, that was exactly the right level of excitement given what they’ve just achieved. It’s rather more involved than bending over and balancing a glass on your arse.

remember that the gravitational pull is so weak, that the equivalent of dropping a football and it bouncing a few cm on earth would be a massive distance on a comet.

saw a few of those comments on the beeb, but I refuse to even reply. if you call the cost of a pint spread over 20 years a complete waste of money then fair enough. that’s your financial contribution, if you’ve been a taxpayer for the last 2 decades.

plus it said EU. this is an ESA project. not EU.

@WackoAK – great INFOGRAPHIC 😀 thanks!

fantastic news its down –

can they retry the arm screws or harpoons to try and make it “safe”?

I reckon its landed on its side.

This is what you want, on board image just posted on twotter

Looks exactly like a Welsh quarry.

Russell T Davies and Steven Moffat will be pleased.

Thats superb

Cheap actually.

and funnily enough, much of that €3.50 was paid to Airbus UK, Airbus Germany, and Airbus France, and then to its employees, where ca. 30% of it went straight back as tax to the governments that paid the €3.50 in the first place, all approximately in line with the geographical contribution.

@andy
so, its a bit like those fines on the Banks,
they government takes that money
the banks increase their prices to us
so effectively we are paying the fines.

rosetta – cheap as chips!

ooooooo it might be in a hole or over on its side and battery could be running low, might need to be moved

i love the twitter feed where its like its a real person ……….

The XKCD thing now has its own domain, if you missed it first time.

http://xkcd1446.org/#0

Give it a moment to load properly and then use right-arrow to step through the frames.

Looks exactly like a Welsh quarry.

Russell T Davies and Steven Moffat will be pleased.
Well played 😆

I’m still reading the BBC HYS comments with a mixture of amusement and depression.

If you go there then you can watch, in real time, the birth of conspiracy theories explaining how this whole thing is an elaborate hoax and hasn’t actually happened.

At least JHJ has been busy 😉

Bit of a controversy over shirt with pvc clad girls – can’t accuse that scientist of being PC

link

this mans going to be the latest “12 months on tv star”

andytherocketeer – Member

it’s a secure area, never use screensaver or lock.

Being a secure area won’t stop me from ctrl-alt-downing you

One thing that puzzles me that I haven’t seen answered anywhere, is will the ratio of sunlight to shade alter as the comet orbits the sun?
I get that it is not getting enough hours of sunlight where it is, although there is a chance it will get more as the comet approaches the sun.
As I understand it, they were expecting Philae to stop working when it got too hot through being too close to the sun.
If it’s in the shade, does that mean it will have a longer life?

Also, is the comet rotating on it’s axis?
Does it have day and night, like a planet?
Is it rotating in relation to the sun, or does it always face the same way, like the moon orbiting the earth?
This seems quite important to me, as the lack of sunlight is the main problem facing Philae, yet there’s no proper explanation anywhere of whether that might change, unless I’ve missed it.

^ unless the orbit of the sun is perfectly spherical and it is spinning on an axis perpendicular to the sun, then it will experience seasons, like earth and the amount of sunlight will vary.

back2basics – Member
i love the twitter feed where its like its a real person ……….

Yep enjoying that too, it’s been done really well:

Philae Lander @Philae2014
.@ESA_Rosetta I’m feeling a bit tired, did you get all my data? I might take a nap… #CometLanding

Turns out it’s day is 12.4 hours long.
http://en.wikipedia.org/wiki/67P/Churyumov%E2%80%93Gerasimenko
With a year of 6.4 earth years, I don’t suppose the seasons will vary much during this mission.

MTG: That is exactly the hope of the guys at ESA – that the changing “seasons” of the comet will bring more sunlight onto the lander and wake it up at some point in the future.

As the comet approaches the sun, it will also become more volatile, and movements/gas-ejections from the comet may disturb the lander and, potentially shift it out of the shade.

Discussed in lots of places: http://www.bbc.co.uk/news/science-environment-30062346

it’s also about 4x away from the sun than we are (give or take), so that’s 1/16th of the solar energy

think any wake up depends entirely on whether the current solar is enough to keep battery heaters ticking over.

Battery heaters?
That hints at an answer to another question from my oversimplified understanding of space exploration…
If I need to plug my bike lights, phone or whatever in to the charger for 7 hours a night last my intended use each day, then if I was only able to plug them in for 1.5 hours, I would have to limit myself to only using them every fifth day.
All the talk is of Philae shutting down completely because the solar panels are not getting enough sunlight, not just doing less to conserve what battery charging it does get.
I take it there’s a minimum charge level needed just for housekeeping, before it’s got any to spare for running equipment?

Good point about the gas ejections too.
I remember reading that the Japanese tsunami shifted the earth on it’s axis slightly.
I guess something more irregularly shaped and less homologous with no atmosphere and on a much more elliptical orbit is far less stable than a planet.

@ midland. Batteries work less well when cold, you must have experienced that. Applies to your phone etc. I think the danger (reality) with landsr is that it will get insufficient light to even maintain a standby mode, insufficient to heat batteries to attempt to “wake up” etc and it will “die” permanently

Yeah, I guessed it would be something like that, and of course, my idea of cold, riding a bike in winter in the UK, is probably a bit different to that of a spacecraft flying 4AUs from the sun. 😉

soes itz dedz then????
as great as the landing attempt was, would questions be asked as to why drills and harpoons didnt work? cos its my understanding the original landing zone would have been perfect….